Blood dendritic cell antigen 2 (BDCA2) is a C-type lectin expressed on human plasmacytoid dendritic cells (pDCs) (Dzionek et al., J. Immunol., 165:6037-6046 (2000)), a specialized population of bone marrow-derived cells that secrete type I interferons (IFNs) in response to toll-like receptor (TLR) ligands. BDCA2 consists of a single extracellular carbohydrate recognition domain (CRD), which belongs to the type II C-type lectin group, at its C-terminus, a transmembrane region, and a short cytoplasmic tail at its N-terminus that does not harbor a signaling motif. BDCA2 transmits intracellular signals through an associated transmembrane adaptor, the FcεRIγ, and induces a B cell receptor (BCR)-like signaling cascade.